Prevalence and VP1 Gene Evaluation Analysis of Porcine Sapelovirus in Yunnan Province, China, from 2024 to 2025.

Porcine Sapelovirus (PSV) is widely prevalent in pig herds throughout the world and induces diarrhea, encephalomyelitis, respiratory tract symptoms, and reproductive disorders. However, the epidemiological and genetic evolution characteristics of PSV remain unclear in Yunnan Province. In this study, 1622 fecal samples were collected from pig farms in Yunnan Province. PSV and its co-infection rates with other pathogens were detected; then, the PSV VP1 gene was amplified and sequenced; and the genetic evolution characteristics of the VP1 gene were analyzed. The overall infection rate of PSV in Yunnan Province was 36.50%, and the differences among regions were significant (p < 0.05). The positive rates among different seasons were significantly different (p < 0.01), ranging from 73.33% (autumn) to 19.00% (summer). The PSV positive rate in diarrhea samples (47.26%) was significantly higher (p < 0.001) than that of non-diarrhea samples (31.77%). The co-infection rates of PSV with porcine rotavirus (PoRV) and PSV with porcine epidemic diarrhea virus (PEDV) were 5.07% and 3.04%. A total of 36 VP1 sequences were obtained, and the average identity among the 36 sequences was 85.3%, which was higher than that with other reference strains. Phylogenetic analysis revealed that all 36 PSV strains belonged to the PSV-1 genotype. The VP1 gene was under strong negative selection pressure (average dN/dS = 0.0838); however, the 95th amino acid was under positive selection pressure. Our study revealed the epidemiological, co-infection, and genetic evolution characteristics of PSV in pig herds of Yunnan Province, providing more data for preventing and controlling diarrhea pathogens in pigs.